Christine S. Sheppard and Frank M. Schurr
Institute of Landscape and Plant Ecology, University of Hohenheim, 70593 Stuttgart, Germany
Invasions are dynamic processes. Invasive spread causes the geographical range size of alien species to increase with residence time. However, with time native competitors and antagonists can adapt to invaders. This build-up of biotic resistance may eventually limit the invader’s performance and reduce its range size. Using a species‐for‐time approach, we test (i) whether native communities more strongly reduce the fitness of immigrants with longer residence times, and (ii) whether the range size of immigrant species shows a unimodal response to residence time.
For 352 plant species in the Asteraceae family with a wide range of minimum residence times in Germany (6,000–18,000 years), we combined a common garden experiment with historical and macroecological analyses. In a multi‐species experiment, we quantified the effect of native communities on fitness components of 30 annual Asteraceae. For these and other species, we then analysed how current range size depends on minimum residence time and other covariates.
Native communities reduced survival, reproductive output and fitness of Asteraceae. This fitness reduction was stronger for immigrant species with long residence times. We found a unimodal relationship between range size and residence time of Asteraceae in Germany, when including natives that immigrated after the last glaciation. Biotic resistance may limit the performance and geographical ranges of immigrant species over long time‐scales. The initial advantages invaders have over natives thus may not persist over millennia, supporting the concept of an alien-native species continuum defined by gradual changes in eco-evolutionary processes. While our analysis controlled for major ecological, evolutionary and biogeographical factors, it is conceivable that the detected patterns are influenced by additional differences between natives and aliens. Experimental macroecology has a great potential to disentangle these processes and predict long‐term invasion dynamics.
Sheppard C. S. & Schurr F. M. (2019) Biotic resistance or introduction bias? Immigrant plant performance decreases with residence times over millennia. Glob. Ecol. Biogeogr. 28: 222–237.